Documents / Report
The Defense Intelligence Agency issued this Defense Intelligence Reference Document (DIA-08-0911-012), dated 14 December 2009, as one of its FY 2009 advanced technology reports under the Advanced Aerospace Weapon System Applications (AAWSA) Program. It reviews how metallic glasses are structured and processed, their mechanical properties, and metallic glass matrix composites. It concludes that dendritic composites could replace high-strength steels in some aerospace parts. It adds that wide aerospace use depends critically on developing new lightweight glass-forming alloys.
“metallic”29 pages
UNCLASSIFIED,',SFQR: 8PPlll'2L t.tl!IE e,ttY Metallic glass foams (see above) also provide Intriguing possibilities for structural applications. It has recently been-shown that metallic glass foams with outstanding strength can be formed by controlling the size of the ligaments between pores. 40 This is a new development, and these foams have not been fully characterized, but it seems likely that optimized foams will have a specific stiffness (E/p) superior to that of polymer foams, along with high strength and acoustic damping. Such structural foams could be useful in applications requiring strength and stiffness under compressive loads, such as structural panels for extraterrestrial buildings. Conceivably, such structural foams might even be produced an site (from raw feedstock), reducing the volume of material that needs to be launched. A final possibility is that metallic glasses might be combined with polymer composites into metal-fiber laminate materials. Similar laminates (with crystalline aluminum alloys) are being employed in large quantities on the new Airbus 380 and are likely to find increased application in the future. 41 The use of metallic glasses in these laminates is appealing because of their high specific strength (although the specific stiffness is lower than that of aluminum). Furthermore, the individual layers in the laminate are sufficiently thin that a wide range of glass-forming alloys might be considered (in contrast to thicker structural sections, which will be limited by the glass-forming ability of the alloy). OTHER APPLICATIONS Monolithic metallic glasses are unique among metallic materials in having no microstructure at length scales of more than a few atomic spacings. In principle then, metallic glasses should be capable of replicating features down .to this scale. This possibility is facilitated by the ability of metallic glasses to be formed in the supercooled liquid temperature range with controllable viscosity. Indeed, superplastic forming of metallic glass surfaces with features as small as 13 nanometers has been demonstrated.42 This ability could be exploited for direct embossing of nanostructures in polymers or other materials. Structures on this length scale are also potentially useful as diffraction gratings for ultraviolet and soft x-ray radiation. In a related area, metallic glasses have a variety of useful properties for application in micro-electromechanical system (MEMS} actuators, including large elastic strains and high resilience (elastic strain energy storage), good corrosion and wear resistance, and an excellent surface finish. 43 The scale of these devices is smaller than the plastic zone size (Equation 1 above), making brittle fracture.unlikely. Furthermore, a much wider variety of amorphous alloys can be made In thin film form (by vapor deposition) than is possible by casting. Finally, the magnetic properties of certain amorphous alloys have long been exploited. For instance, their low coercivity and high electrical resistivity make ferromagnetic amorphous alloys attractive as high-efficiency electrical transformers, particularly at high frequencies. Such applications are likely to continue well into the future. 19 UNCLASSIFIED/,'FOA 8FFIGll2L 1181 8Nklf
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Report, from the dia collection. The PDF is mirrored here; the original link is under it. 30 pages are in the text index: search them above, or from the library's search.